The prognostic value of weight loss during radiotherapy among patients with nasopharyngeal carcinoma: a large-scale cohort study

BACKGROUND: We aim to investigate the prognostic value of weight loss during radiotherapy (RT) among patients with nasopharyngeal carcinoma (NPC). METHODS: A total of 1149 NPC patients who received radical RT were retrospectively analyzed. Patients’ weight were measured at initiation of RT (W(Pre-RT)) and every week during RT (W(RT1,2,3,4,5,6,7)). Percentage of weight loss (PWL) at 1st, 2nd, 3rd, 4th, 5th, 6th, and 7th week of RT (RT-PWL(1,2,3,4,5,6,7)) were calculated using the following equation: (W(Pre-RT) –W(RT1,2,3,4,5,6,7))/W(Pre-RT) × 100%. The optimal threshold of RT-PWL(7) was determined by recursive partitioning analyses (RPAs). Our endpoints included disease-free survival (DFS), overall survival (OS), distant metastasis-free survival (DMFS), and locoregional relapse-free survival (LRRFS). RESULTS: The median RT-PWLs were 0, 0, 1.5, 2.9, 4.1, 5.5, 6.6% at 1st, 2nd, 3rd, 4th, 5th, 6th, and 7th week of RT, respectively. RT-PWL(7) optimal threshold with respect to DFS was 5.3% based on RPAs. Therefore, a consistent threshold of 5% (<5% vs > ≥5%) was selected to classify NPC patients into low RT-PWL(7) and high RT-PWL(7) groups for survival analysis. Compared to high RT-PWL(7) (≥5%), patients with low RT-PWL(7) (< 5%) had significantly better ten-year DFS (61.2% vs 78.8%; P < 0.001), OS (70.1% vs 86.6%; P < 0.001), and DMFS (80.2% vs 88.5%; P = 0.007). However, no difference was observed between LRRFS groups (91.7% vs 94.3%; P = 0.173). In multivariate analysis, high RT-PWL(7) was an independent risk factor for DFS (HR, 1.56; 95%CI, 1.19-2.03; P = 0.001), OS (HR, 1.54; 95%CI, 1.11-2.15; P = 0.011), and DMFS (HR, 1.47; 95%CI, 1.03-2.10; P = 0.033) in patients with NPC. In addition, treatment strategy, plasma Epstein-Barr virus DNA, and N stage were associated with weight loss. CONCLUSIONS: High RT-PWL(7) was significantly associated with decreased DFS, OS, and DMFS for NPC patients. Clinicians should continuously inform patients on the health impact of minimizing RT-PWL(7) under 5% during radiotherapy.